Fourier spectrum to recover deterministic and stochastic behavior in stirred tanks

Velocity data from the impeller region of Rushton and 6SRGT pilot-scale imp ellers were analyzed both in the frequency domain and with respect to perio dicity. The four characteristic frequencies and their combination were dete cted from the Fourier spectrum, and the deterministic part of the signal wa s recovered by making the amplitude of the other frequencies zero. The dete rministic part was then analyzed with tools from nonlinear theories. For th e two turbine-types, the dynamics of the deterministic velocity parts were almost identical. The turbulent part of the signal could also be estimated in a similar manner.